TRANSACTIONS OF THE AMERICAN INSTITUTE OF MINING ENGINEERS 
[subject to revision] 

DISCUSSION OF THIS PAPER IS INVITED. It should preferably be presented in person at the 
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Unless special arrangement is made, the discussion of this paper will close April 1, 1917. Any discussion 
offered thereafter should preferably be in the form of a new paper. 


Geology of the Iron-Ore Deposits of the Firmeza District, Oriente 

Province, Cuba 

/ 

BY MAX ROESLER, PH. D.,* SANTIAGO DE CUBA, CUBA 
(New York Meeting, February, 1917) 


TABLE OF CONTENTS 

Page 

I. Introduction...1790 

Location. J. .1790 

Scope of Work and Acknowledgments.1791 

History and Mining , • • </.1792 

II. Topography and its Interpretation.1792 

III. Petrology. 1794 

Sedimentary Roc^.1794 

Descripti^.1794 

Age. . . ^ .1796 

Igneous Rocks . 1797 

Diabasic Rocks .yj. .1798 

Dioritic Rocks ^ .1799 

Granitic Rocks • V ^.1800 

Later Dike Rocks.1800 

IV. Areal Geology.1800 

Rock Types Found in the District.1800 

Distribution of the Various Rock Types.1801 

Surface Distribution.1801 

Vertical Distribution..^ ..... . 1802 

Causes of Present Areal and Vertical Distribution of the Various 

Rock Types.1803 

Faulting.1803 

Magmatic Differentiation.1803 

Tilting.1807 

Erosion.1808 

V. General Description of Ore Deposits.1808 

Nature of Ore.1808 

Shape and Size of Orebodics.1808 

Y Geologic Position.1809 

Mineralogy.1810 

Distribution. 1810 

Interpretation.1811 

Superficial Alteration.1814 

'b of the Ore Deposits.1816 

yious Theories.1816 

J. P. Kimball. 1816 


legist, Spanish American Iron Co. and Juragua Iron Co. 


I 


« I 









































1790 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


, Paqb 

F. F. Chisholm.1816 

A. C. Spencer.1816 

J. F. Kemp.1817 

W. Lindgren and C. P. Ross.1817 

J, T. Singewald and B. L. Miller.1818 

Present Hypothesis.1818 

Source of the Ore.1818 

Vehicle to Carry the Ore.1819 

Channels of Access.1819 

Causes of Deposition.1819 

Discussion of Different Hypotheses.' 1821 

VII. Detailed Description of Ore Deposits.1825 

Ocania Mine.1825 

West Five Mine.1828 

Loma Alta Mine.1829 

West Three Mine.1830 

West Four Mine.1830 

West One Mine.1830 

East Mine.1831 

Chicharron Mine.. . 1832 

Estancia Mines.1834 

Concordia Mine.1834 

VIII. Geologic History ...” .1834 

Sedimentation.1835 

Igneous Cycle.1835 

Uplift, Tilting and Erosion.1836 

Deposition of Coral Limestone.1837 

Emergence ..1837 

Submergence.1837 

IX. Economic Application.1837 

Continuation of the Orebodies in Depth.1838 

Character of the Ore in Depth.1838 

Favorable Locus for Exploration Work.1838 

X. Bibliography.1839 


I. INTRODUCTION 

The following article concerns the geological occurrence of the iron- 
ore deposits on the south coast of Cuba. The article is based on a de¬ 
tailed field study, made in the hope that some information would be 
gained which might be of value in the search for further orebodies, or 
in the economic development of the ore already found. 

Location 

The iron-ore deposits of the Firmeza district lie near the 
the southeastern part of Cuba, in the Province of Oriente 
bodies of this district form part of a belt of deposits that ^ 

Sigua, 25 miles east of Santiago, to Sevilla, 5 miles east of 
lies on the seaward slope of the Sierra Maestra rang^ 






































MAX ROESLER 




1791 


This range roughly parallels the coast in the southern part of Oriente 
Province. Its crest is about 6 miles north of the mines near Firmeza. 
The town of Firmeza lies 9 miles east of Santiago, and about 23^ miles 
from the Caribbean Sea. The mines included in the Firmeza district 
are the Ocania Mine and a group of mines that extends from West Five 
Mine to the Concordia Mine. The elevation of the mines is from 400 
to 1,000 ft. above sea level. Their exact location is shown on the map 
(Fig. 1) which is a copy of a map furnished by the Juragua Iron Co. 

Immediately east of the Firmeza district lies the Daiquiri district of 
the Spanish-American Iron Co. 



Fig. 1. 

Scope of Work and Acknowledgments 


Detailed examinations have been made by J. P. Kimball,^ A. C. 
Spencer,2 and J. F. Kemp,^ and many others have contributed to our 
knowledge of the deposits. The writer has made use of all the available 
information and will endeavor to give full credit for it. 

The present article has been written under the first award of the 
S. F. Emmons Memorial Fellowship, and the writer takes this occasion 
to thank the committee in charge of the fellowship for their assistance 
and criticism. Thanks are also due to the Juragua Iron Co. for permis¬ 
sion to make the examination, for the use of their maps, and for their 
kindness in giving access to all the available data and facilities. The 
Spanish-American Iron Co. also made possible the visiting of neighboring 


‘ L2,3^00 Bibliography at end of paper. 









1792 IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 

properties and most grateful acknowledgment is hereby made to the 
officials and staff of both companies. 

The Geological Faculty of Yale University, and Professor C. P. 
Berkey of Columbia University, have been freely consulted on different 
phases of the problem, and their advice has been of much service. 

History and Mining 

The Firmeza orebodies have been worked continuously since 1884, 
except for a short period during the Spanish-American war, and the 
total production of the mines, from 1884 to 1913 inclusive, has been 
6,776,171 tons.^ The mines of the Firmeza district belong to the Juragua 
Iron Co., which is now controlled by the Bethlehem Steel Co., though 
it was at one time also allied with the Pennsylvania Steel Co. 

The mining of the ore and the stripping of the overburden is done 
by steam shovel. Where the orebody is small or intimately associated 
with waste, it is found advantageous to lease the workings to contractors 
and pay for the ore on the basis of tonnage and grade, delivered in mine cars. 

The ore from the mines is put through the crusher at Firmeza, from 
which the major part is shipped direct to La Cruz, the company’s shipping 
point on Santiago harbor. A small part of the output, high in sulphur, 
is roasted in the valley south of Firmeza, near Siboney, before it is shipped 
to La Cruz. 


II. TOPOGRAPHY AND ITS INTERPRETATION 

The topography of the Firmeza district falls naturally into three 
main divisions which have a lateral extent parallel to the sea coast and 
the main range of the Sierra Maestra,—that is, in an east-west direction. 
Beginning at the coast there is a range of terraced cliffs rising to uniform 
height of about 300 ft. The terraces all face the south, to the sea, and 
appear to be of wave-cut origin, excavated in flat-lying coral limestone. 
There is no beach, the sea beating directly against the limestone cliffs, 
except at the mouth of the Rio Carpintero at Siboney, where there is a 
small beach made up of coral fragments and an arkosic sand in which 
feldspar predominates. 

Back of the terraces there is a fairly gentle landward slope to a silt- 
covered, flat, east-west valley. In this valley the streams from the 
mountains are generally lost in lagoons and swamps. Some of the larger 
ones, such as the Rio Carpintero, And their way to the Caribbean through 
comparatively narrow gorges cut in the cliffs that border the sea. These 
streams appear to be of an intermittently torrential type. In the dry 
season they show very small streams of water flowing through stream 
beds covered with boulders up to several tons in weight. 


* D. B. Wliitaker: Engineering and Mining Journal, vol. 97, p. 677 (1914). 



MAX ROESLER 


1793 


North of this valley rise the foothills of the Sierra Maestra—sharp, 
steep hills, covered as a rule with dense forest growth. They are con¬ 
nected with the main range of the mountains by ridges that have steep 
slopes and narrow crests. The connecting ridges are less heavily forested 
than the foothills but are covered with high grasses and an occasional 
grove of trees. The mountains themselves are thickly covered with 
pines and rise to an elevation of about 3,500 ft. 

The limestone cliffs, with their sea-cut terraces, have been interpreted 
as evidence of periodic movements of the island, but it seems to the writer 
that the widespread occurrence of a terrace about both Jamaica and 
Cuba at the same elevation above sea level indicates a movement of the 
sea surface, rather than of the land. 

In speaking of the Seboruco (the local name for the coastal limestone) 
R. T. Hill says:^ 

“Nowhere have I seen the elevated reef rock folded or otherwise disturbed except 

by the gently sloping coastward inclined elevation it has undergone.-The Seboruco 

as a whole represents a recent and uniform elevation of the whole periphery of the 
island-“ 

The following terrace elevations have been taken from the report 
of C. W. Hayes, T. W. Vaughan, and A. C. Spencer,® and arranged in 
tabular form by the writer: 


Havana, 

Feet 

Matanzas, 

Feet 

Gibara, 

Feet 

Baracoa, 

Feet 

Manzanillo, 

Feet 

Santiago, 

Feet 

4-5 

5-6 

5-20 

5-6 

5-20 

20 

10-15 

30 

40 

90 

100 

100 

100 • 

140 

100 

250 

200 

280 

200 

200 

150-180 




300 










R. T. HilF in the report on Jamaica has given less definite figures for 
the terrace elevations, and the following conclusions: 

“In general the oldTeef rock of Jamaica consists of three distinct formations, 
occurring at three levels, 70, 25, and 10 ft. (or less) respectively. From the per¬ 
sistency of these three levels on the north, east and southwest end of the island, it is 
evident that their present position above the water is due to continuous epeirogenic 
elevation after the present outlines of the island had been chiefly defined.” 

For Hayti and Porto Rico no exact data are available to the writer. 


® R. T. Hill: Notes on the Tertiary and Later History of the Island of Cuba. 
American Journal of Science, Ser. 3, vol. 48, p. 203 (1894). 

« Op. cit. (in Bibliography), pp. 18, 19. 

^ R. T. Hill: Geology of Jamaica. Bulletin of the Museum of Comparative Zoology 
at Harvard, vol. 34, pp. 92-100 (1899). 





























1794 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


The data quoted show that on the north, northeast, and southeast 
coast of Cuba, and on the nor.th, east, and southwest coast of Jamaica, 
there is a marine terrace from 5 to 20 ft. in elevation. It seems to the 
writer that this evidence might suggest that, at least in part, the differ¬ 
ential movements of land and sea in Cuba have been due to movement of 
sea level rather than of land surface. The slight variations in elevation 
would then be explained by unequal erosion of the gently sloping surface 
of marine planation. The slight seaward slope of the coast limestone, 
in the neighborhood of Santiago, is no greater than is to be expected 
of a near shore surface of marine planation. 

There is further evidence of emergence of the island, in respect to sea 
level, in the tuff-limestone found at an elevation of about 1,400 ft., and 
the steep-sided, sharp, mountain topography points to fairly recent 
rejuvenation. 

The silt-covered, east-west valley, in which the streams are aggrad¬ 
ing, suggests that the last movement of land with respect to sea level has 
been a downward one, and this is in accord with the evidence of the 
harbors of Santiago and Guantanamo, which have been interpreted as 
bays formed by drowning.® 

The topography seems to be almost entirely independent of the lith¬ 
ology. An exception to this is the coarse crystalline marble that forms 
a capping to many of the foothills. Apparently the massive marble offers 
greater resistance to tropical weathering than do the fine-grained, dia- 
basic or dioritic rocks which marmorized it, for the arroyos are cut into 
the latter. The occurrence of marble as a capping is too frequent to be 
entirely fortuitous. 

III. PETROLOGY 
Sedimentary Rocks 
Description 

The sedimentary rocks are represented in the Firmeza district entirely 
by limestones. At the coast, and rising in three sea-cut terraces to an 
altitude of about 350 ft., are recent limestones. According to the report 
of Hayes, Vaughan, and Spencer,^ this rock is 

“replete with the remains of numerous species of corals which are all, so far as 
examined, at present living in the surrounding Antillean seas.” 

There seems to be one rather striking point of difference between the 
higher landward terraces and the lower terrace bordering the Caribbean. 
This is, that while all three terraces contain coral remains, the landward 

® Hayes, Vaughan, and Spencer, Op. d/., p. 17. 

® Op. cit. pp. 23-24. 





MAX ROESLER 


1795 


terraces are almost entirely massive, while the seaward terrace is made up 
of more loosely cemented coral remains. On the land, where the lime¬ 
stone comes into contact with the underlying igneous rock, there are 
boulders of rock and of iron ore cemented by the lime, showing that 
erosion of the orebodies had begun before these coral rocks were formed. 

In the foothills of the Sierra Maestra, which vary in altitude from 
600 to 1,300 ft., there occur, usually as a capping on the hilltops, bodies 
of massive limestone now largely marmorized. Bedding is almost 
entirely lost, but where thinner masses have been involved in the volcanic 
rocks it is possible to discern a pitch toward the southeast at an angle 
of about 30°. The freshest pieces of this limestone, taken from boulders 
on the north side of the hill north of West Five Mine, show it to be a 
blue, dense, fine-grained limestone. The microscope shows no evidence 



PiQ^ 2 .—Tuff-Limestone from Ridge Connecting Foot Hills with Main 
Range of the Sierra Maestra. Limestone—groundmass. Plagioclase frag¬ 
ments—white. Volcanic rock fragments—dark. X 18. 

of organic remains in the thin section, but only a granular aggregate of 
calcite. 

On one of the ridges connecting the foothills with the main range, 
at an elevation of about 1,400 ft., an unaltered limestone of unusual type 
was found. This rock has the deeply pitted surface typical of the weath¬ 
ered outcrops of all the limestone in this region. The color of the rock 
on a fresh fracture surface is blue-gray. Closer examination shows 
minute areas with a vitreous luster embedded in a granular calcite 
matrix, giving to the rock the appearance of a porphyry. A thin section 
of the rock shows that the crystals are fragments of plagioclase, of about 
andesine-labradorite composition. There are also angular fragments of 
a diabasic rock (Fig. 2). The fragments are all about 0.5 mm. in diame¬ 
ter, and their presence in the limestone shows that the sediment was 



1796 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


formed at a time of volcanic activity on the adjacent land. The perfect 
freshness of the feldspars is probably due to the fact that the sea water 
was already saturated with calcium carbonate, and so was not chemically 
active in so far as the calcic feldspars were concerned. The ferromag- 
nesian minerals of the diabasic fragments are entirely altered. This 
tuff-limestone seems to be very similar to that described by C. P. Berkey^® 
among the “probably” pre-Tertiary rocks of Porto Rico. 

Age 

The nature of this rock shows that at least part of the volcanic 
activity was contemporaneous with the sedimentation. As the andesitic 
rocks accompanying this tuff-limestone are believed to represent the 
initial stages of the igneous cycle, the determination of the age of the 
sediment must also fix the age of the igneous rocks. 

The age of these limestones and the associated volcanics has been a 
rather vexed question. J. F. Kemp speaks of an article by H. Wedding,“ 
in which he places them in the Jurassic, in the horizon of Quenstedt’s 
Beta, of the upper White Jura. This determination was made upon 
material furnished by G. W. Goetz, The only other definite information 
on this subject of age is that given by J. T. Singewald, Jr., and B. L. 
Miller. They found a fossiliferous limestone in the Daiquiri district, 
and submitted some of the fossils to T. W. Vaughan, who correlated one 
of the species with the Cretaceous of Jamaica and determined the age 
of the limestone as “Mesozoic, probably Cretaceous.” 

W. Lindgren^^ says: 

“The idea of the geologists who have done the most work in this section seems 
to be that the lavas and tuffs and associated limestones are of Eocene age-.” 

R. T. Hill,^'^ speaking of the volcanic elastics of the Jamaican Blue 
Mountain Series of Cretaceous age, says: 

“In Cuba these clastic rocks constitute the high divides of the Oriente-.“ 

Experience during historic time shows that it would not be justifiable 
to infer volcanic activity in one of the islands of the Antilles on the basis 
of such activity in another. In the present case there is, however, the 
evidence of Cretaceous sedimentation in Jamaica determined by R. T. 
Hill, the direct correlation of the Daiquiri specimen with the Jamaican 

C. P. Berkey: Geological Reconnaissance of Porto Rico. Annals of the New 
York Academy of Sciences, vol. 26, p. 20 (1915). 

“ H. Wedding: Die Eisenerze der Insel Cuba. Stahl und Eisen, vol. 12, No. 12, 
pp. 545-550 (June 15, 1892). 

^2 J. T. Singewald, Jr,, and B. L. Miller; The Genesis and Relations of the Dai¬ 
quiri and Firmeza Iron-Ore Deposits, Cuba. Trans., vol. 53, pp. 67-74 (1916). 

W. Lindgren and Clyde P. Ross: The Iron Deposits of Daiquiri, Cuba. Trans. 
vol. 53, p. 41 (1916). 

R. T. Hill: The Geology and Physical Geography of Jamaica. Bulletin of the 
Museum of Comparative Zoology at Harvard, vol. 34, p. 170 (1899). 










MAX ROESLER 


1797 




fauna by T. W. Vaughan, and R. T. Hilhs reference to the clastic rocks 
of Oriente. E. T. Hodge has informed the writer that he found Comanche 
fossils among the pre-Tertiary. 

Igneous Rocks 

The igneous rocks of the Firmeza district form a natural series of 
differentiation products from a basic magma. They range from a fine- 


4^_Diabase Porphyry with Epidote-Filled Amygdule. From Railroad 

Cut Opposite West One Mine. X 18. 

grained diabase to a highly quartzose aplite. J. F. Kemp^^ has given a 
discussion of the nomenclature used in former articles on the district. 

The Geology of the Iron-Ore Deposits In and Near Daiquiri, Cuba. Trans., 
vol. 53, pp. 3-38 (1910). 


Fig. 3.—Diabase Porphyry with Included Fragment of Earlier Volcanic 

Rock. West Four Mine. X 18. 



1798 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 




For purposes of mapping, the writer divides the igneous series 
into four groups: 

1. The diabasic rocks. 

2. The dioritic group. 

3. The granitic group. 

4. The later dike rocks. 


Fig. 5.—Diokite from Level 1 of West Five Mine. Cros ed Nicols. X 18. 


Fig. 6.—Quartz Diorite from East Mine. This is the Basic Member of the 

Granitic Series. Crossed Nicols. X 18. 

Diabasic Rocks 

The diabasic rocks are fine-grained, as a rule, and porphyritic. They 
are the representatives of the original magma. Megascopically they are 
dense, dark rocks. Under the microscope they show as felty aggregates 
of plagioclase laths with interstitial ferromagnesian minerals. They are 




MAX KOESLER 


1799 


usually fragmental (Fig. 3) and frequently show epidote-filled amygdules 
(Fig. 4). _ ^ 

These diabasic rocks show a bedded structure in places, with inter¬ 
calated limestones and are undoubtedly in part extrusives. 



Fig. 7.—Granite Showing Micrographic Quartz Feldspar Intergrowth about 
Plagioclase Nucleus. From the Juragua Valley. Crossed Nicols. X18. 


Dioritic Rocks 

The wall rock of many of the orebodies is a gray, fine-grained, and 



Fig. 8.—Specimen B from Dike in West Side of West Five Mine. Eleva¬ 
tion 520 Ft. Note Corrosion of Plagioclase and Dominance of Quartz. 
Crossed Nicols. X 18. 


even-textured rock. Plagioclase, varying from labradorite to bytownite, 
is the most abundant mineral, with much hornblende between the feld¬ 
spars. On the basis of the feldspars it is a gabbro, but in the older 




1800 lUON-ORE DEPOSITS OF THE FIllMEZA DISTlilCT 

classification the hornblende makes of the rock a diorite. Since that 
terminology has been adopted* by earlier writers on the district it is 
accepted here. Fig. 5 shows a typical diorite. 

The diorites and diabases are frequently found merging into each 
other without any visible contact. Both are the hosts of the orebodies. 

Granitic Rocks 

J. F. Kemp^® has used the term granite for the quartz-bearing dio¬ 
rites and the true granites “to avoid all confusion of this rock with the 
diorites which are associated with the ore.” That usage is adopted 
in this paper, and the scope of the term granitic rocks is enlarged to 
include the aplites and quartz porphyries. This inclusive usage seems 
justified by the fact that the quartz-bearing rocks form a group later 
than the ore-bearing rocks, though pre-mineralization. 

All the rocks of this group are hornblende-bearing except the most 
acid aplites, and even the most acid show very little potash feldspar. 
The basic members of the series are gray, coarse-grained, feldspathic 
rocks (Fig. 6) while the acid members are made up of striking feldspar' 
quartz intergrowths (Fig. 7), or else are fine-grained quartz aplites (Fig. 
8). The extremely rapid variation in chemical composition is shown by 
three microscopic analyses of rocks from the same dike at different 
elevations and ascending order. 



Feldspar 

Quartz 

Ferro mag. 

Magt. 

A. 

61.8 

28.0 

5.5 

4.7 

B. 

54.0 

41.6 

3.4 

1.0 

C. 

52.7 

■ 45.2 

1.1 

1.1 


Later Dike Rocks 

The entire mineralized area is cut by basic dikes that vary from 
basalt to andesite. They are post ore, but usually carry pyrite. A 
detailed description would serve no definite purpose in this connection. 

IV. AREAL GEOLOGY 
Rock Types Found in the District 

The study of the petrographic features shows that there are several 
types of igneous rocks and two limestone formations in the Firmeza dis¬ 
trict. The igneous rocks form a continuous series from diabasic extru¬ 
sive and intrusive rocks, through diorite and granite, to highly acid 


Op. cit., p. 12. 





















MAX ROESLER 


1801 


aplites. This series is cut by dike rocks of various types, which range 
in composition from basalt to andesite. The sedimentary rocks fall 
naturally into two divisions;—earlier marmorized limestone, probably 
Cretaceous in age, and now exposed only in scattered outcrops, and 
younger recent coral limestones depositee^ as a fringe on eroded igneous 
rocks. 


Distribution of the Various Rock Types 
Surface Distribution 

The two appended maps show the surface distribution of the rocks 
and orebodies. Owing to the lack of topographic maps, and the diffi¬ 
culties attending work in an area covered by tropical verdure, they can¬ 
not lay claim to great accuracy of detail. Future work will undoubtedly 
shift the contacts in many places and add a number of dikes. But enough 
work was done, and enough outcrops plotted to justify the making of the 
maps and the belief that they show the general relationship of the forma¬ 
tions. Acknowledgment is made to Dean Corsa, whose unpublished 
map in the possession of the Juragua Iron Co. was in part used. 

The different formations lie, as shown by the map, in belts of irregular 
width, roughly parallel to the coast line. 

Nearest the sea is the belt of coral limestone. This belt is about 
3,000 ft. wide in the area mapped. To the west, where the railroad runs 
to the Ocania Mine, the fringing limestone extends inland nearly 2 
miles. Apparently the width of the belt is largely determined by the 
slope of the pre-deposition erosion surface, the wider belt lying ont he 
more gently sloping surface. 

North of the coral limestone belt, the main mass of granitic rocks is 
exposed. This forms a belt from 6,000 to 8,000 ft. wide. Most of the 
granite area is covered by an alluvial deposit, through which rise knobs 
of the igneous rock. These knobs are all granite, usually with inclusions 
of dioritic material. 

North of the granitic area lies the diorite. This forms a very irregular 
belt on the lower part of the foothills of the Sierra Maestra. From the 
Demajayabo River south of the Concordia Mine, to south of Loma Alta, 
the width of diorite is from 1,200 to 3,000 ft. At West Five Mine the 
diorite area runs back into the hills north of the region mapped. In 
the Juragua valley the diorite is exposed about 1 mile north of Firmeza. 

The diabasic rocks lie higher in the hills than the diorite and in 
general their exposures on the surface are north of the diorite. No attempt 
has been made to show on the map the contact between the extrusive and 
intrusive facies of the diabases. This contact is exceedingly indefinite 
and rarely distinguishable. 


1802 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


Bodies of granitic rock, that differ from the main granite mass, cut 
through the diorite and the diabases in the region mapped. These bodies 
are apophyses of the main granite massif and form dikes, sills, or irregular 
bosses. They lie in a roughly east-west belt in the foothills, and are of 
great importance because the orebodies are scattered irregularly as a fringe 
to these apophyses. This can be seen clearly both on the map of the 
district and on the larger scale map of the mines near Firmeza. 

The older limestones lie in the diorite and diabase area, rarely in 
contact with the granite. They have been metamorphosed to a dense 
marble in the area mapped, and are preserved as irregular masses capping 
the foothills, or as beds interbedded with the extrusive rocks. The out¬ 
crops vary in size from small blocks to areas that are as much as 1,200 
ft. in diameter. An even larger area at the Ocania Mine does not show 
on the map. 

All the formations are cut by the later basic dikes. Except in the 
mines these dikes have not been mapped. They fall into two systems: 
one almost vertical, striking northerly, or slightly east of north; the other, 
an almost horizontal system, that might equally well be classed as a 
system of sills. Petrographically there is no difference between the two 
systems. 

Vertical Distribution 

The vertical arrangement of the different rock types is even more 
marked than their linear distribution, as it shows on the surface maps. 

The coastal limestones rise in terraces to an elevation of about 300 
ft., where they terminate in a flat top. 

The granite massif has an upper surface which rises gradually from an 
elevation of about 350 ft. at the eastern end of the district, to about 700 
ft. at the Ocania Mine. The granitic apophyses, as now exposed, are 
rarely more than 150 ft. above the top of the granite massif, and their 
downward extension where exposed by erosion can be seen to merge 
into the granite. 

The diorite and the diabasic rocks must be considered together, be¬ 
cause, while the lower limit of the diorite is determined by the top of the 
granite intrusion, the upper limit is, as a rule, indeterminate, and the 
diorite merges into the diabases. The two rocks were mapped separately 
in the field and a contact drawn, but it is generally arbitrary. More 
rarely the contact mapped represents an observed intrusive contact. 
As established, the contact between diorite and diabase rises from 500 
ft. elevation in the eastern to 800 ft. at the Ocania end of the area. 
Fragmental igneous rocks are found at 700 ft. in the East Mine, and at 
1,000 ft. elevation at Ocania. No continuous contact between intrusive 
and extrusive diabase was mapped. 

The older limestone masses have not been found in this district, at 


MAX ROESLER 


1803 


a lower altitude than 400 ft. The highest body of limestone examined 
was the tuff-limestone found at 1,400 ft. 

The lack of contour maps makes it difficult to draw accurate sections. 
But the elevations can be tabulated as follows: 


West End of District 
(Ocania Mine), Feet 


East End of District. 
Feet 

1,000 . 

.. .Fragmental igneous rocks. 

. 700 

800. 

... . Diorite-diabase contact. 

. 500 

700 . 


. 350 

300. 

,Top of coastal limestone. 

.!. 300 


This table shows the distinct vertical distribution of the igneous 
rock types, and a well-defined pitch of their surfaces of contact. 


Causes of Present Areal and Vertical Distribution of the Rock Types 

Faulting. —The linear distribution of the rock types, as shown on 
surface maps, suggests at once a direction of major faulting. But except 
for two minor faults in the East Mine, the one northeast-southwest, the 
other northwest-southeast in > strike, and a somewhat larger east-west 
fault in West Five Mine, no displacements worthy the name of fault 
were found in the area. The nearest approach to a fault system is shown 
by the later basic dikes. These, with the one vertical north-south trend 
and a horizontal system, appear to have filled a definite fissure system, 
but there is no evidence of any appreciable movement along most of 
them. In West Five Mine an aplitic dike-is offset 6 in. on the opposite 
sides of a 2-ft. wide basic dike. If the dikes do represent an older fissure 
system, it is a system due to contraction during cooling of the igneous 
rock, rather than to faulting. The Firmeza district must be added to the 
long list of those in which ore deposits are connected with fissures of 
minor or no displacement. 

It is the writer’s opinion that the present areal and vertical distribu¬ 
tion is due to three different causes—magmatic differentiation, tilting, 
and erosion. Each of three must be considered in an attempt to solve 
the problem. 

Magmatic Differentiation. —To show that the vertical distribution of 
the rocks is due to magmatic differentiation it will be necessary to estab¬ 
lish the comagmatic origin of the igneous rocks and their age relationship. 

The detailed petrographic study has shown that there are present in 
the district igneous rocks showing all the stages of a gradual transition 
from diabase porphyry to highly acid aplites. The merging of the types 
can also be found in the field. 

Northeast of Estancia hill the transition of a granite-porphyry sill 
into the main granite and quartz-diorite massif can be followed. There 
is no contact between the two types. The granite massif itself contains 
numerous inclusions of more basic material. These inclusions are an- 










1804 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


giilar, subangular, or rounded. J. F. Kemp^^ found apparently similar 
inclusions in the Daiquiri district and his interpretation is: 

“Apparently the inclusions represent some older solidified rock.” 

With this interpretation the writer does not feel in entire accord. The 
inclusions certainly represent early differentiates, either early crystal 







\-r.* 






















GEOLOGICAL MAP 

orTHC 

FIRMEZA DIST 


ceacNO 

Diabasic Rocks 
Diorite 

Granitic Rocks 
Older Limestone 
Recent Limestone 
Orebodies 

Trails 

Roads 

Railroads 

Contacts 

Orebodies (unidentified) 


CARIBBEAN SEA 


Fig. 9. 


accumulations, or possibly segregations in the still liquid state which 
had an opportunity to crystallize; but either way they are more or less 
reabsorbed portions of the magma itself, and so endogenous inclusions. 


Op. ciL, p. IG. 






































































MAX ROESLER 


1805 


After initiation of crystallization the character of the magma changed 
until it had power to reabsorb part of the already crystallized material. 
The result of the same action was observed on a small scale in a microphoto¬ 
graph of a specimen from the lower part of the aplite dike in West Five 
(not reproduced in this paper). It shows a zonal plagioclase, calcic in 
the central part, sodic at the edges, and much corroded. Obviously 
the plagioclase must have formed before the liquid was of such a composi¬ 
tion that it could corrode it. Similarly it seems possible that, in a slow- 
cooling magma, crystals form and gather in clusters, and the interstitial 
liquid, changing in composition, could reabsorb them more or less 
completely. 

Beside the evidence of the endogenous inclusions, the transition from 
• quartz-bearing to quartz-free diorite can be observed in the upper levels 
of West Five Mine, and that from diorite to diabase in West Four Mine. 
That the extrusive diabases and intrusive diabases are of the same mag¬ 
matic origin can be seen from the complete similarity of the two rocks 
both megascopically and microscopically. The only difference is the 
greater fineness of the ground mass in the volcanics. 

Other features that seem to point toward comagmatic origin of the 
igneous rocks are the almost total absence of orthoclase in the entire 
series, and the predominance of hornblende as a ferromagnesian constitu¬ 
ent. The latter is considered an indication of the presence of abundant 
crystallizers which would aid in holding the magma fluid at comparatively 
low temperature. 

The age relationship of the igneous rocks in a country lacking in 
sediments that are chronologic guides must be determined by intrusive 
contacts. The intrusive nature of the granitic apophyses in the diabases 
and diorites can be established in almost any of the mines. That the main 
granite massif is later than the diorite is well shown in La Posa brook 
just north of its junction with the Rio Carpintero, where dikes of massive, 
even-grained granite cut the diorite. Diorite cutting diabase is seen at 
the contact of the two rocks in the Juragua valley north of the mines. 
Diabase containing fragments of the volcanic diabases is found all through 
the district. 

The order of formation is, then, the normal one from the basic to the 
acid end of the series; i.e.: 

1. Diabasic extrusive. 

2. Diabasic intrusive. 

3. Diorite. 

4. Granite. 

5. Aplite. 

The origin from a common parent magma and the age relationship 
established, it can be shown how this would account for the observed 

7 


1806 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 










































































MAX ROESLEU 


1807 


vertical distribution of the igneous rock types. The series from diabase 
to granite agrees so completely with the series described by N. L. Bowen^^ 
as the normal result of fractional crystallization in a basaltic magma, 
that this mode of differentiation seems to be the probable one in this 
case. 

The diabase extrusives mark the initiation of igneous activity, and the 
diabase intrusive and the diorite mark early chilled phases of a magma 
becoming more and more acid. The granitic massif is believed to be 
the batholythic invasion of the more completely differentiated acid liquid, 
and the granitic apophyses part of the final differentiate from the granite. 
They will be discussed more fully with the genesis of the ore deposits. 



Diorite 
Ora/tit e 


JJ 


ra m /. 




The position of the granite at a definite horizon is thought to be due to 
the fact that the cooled shell of the magma had developed cooling cracks 
to that depth, and as a result the crystallizers were able to escape from the 
granite, which could then no longer remain liquid. 

Thus differentiation may account for the horizontal arrangement of 

the rock types observed in the field. 

Tilting. —However, the arrangement is not entirely horizontal. 

There is a distinct slant toward the southeast of all the surfaces of con¬ 
tact. The extrusives and the limestones, where bedding can be de¬ 
termined, all show a pitch to the southeast. Just when the tilting took 
place is difficult to establish, but since it does not affect the coastal lime¬ 
stone it may be placed as previous to its deposition. 

N. L. Bowen: The Later Stages of the Evolution of the Igneous Rocks. Supple¬ 
ment to Journal of Geology, Vol. 23 (November-December, 1915). 






































1808 


IKON-OKE DEPOSITS OF THE FIRMEZA DISTRICT 


Whether tilting accompanied or followed the igneous cycle and the ore 
deposition cannot be determined. As the orebodies in the eastern end of 
the district are lower than those at the western end, it seems more 
probable that the tilting took place later than the period of ore deposition. 
The evidence is inconclusive and indefinite, but it is unimportant as the 
time of the tilting cannot affect any of the major hypotheses. 

Erosion .—Since the time of ore deposition erosion has produced a 
surface that slopes down in general from the north to the south. In 
this way it has cut across the basic rocks and into the granitic massif. 

Fig. 11 shows a diagrammatic representation of the way the present 
arrangement of the rock types is believed to have been brought about. 
The diagrams are not to scale, and are intended merely as an aid to 
visualizing the conditions. 

Diagram 1. Shows conditions after differentiation and before tilting or erosion. 

Diagram 2. Shows conditions after tilting and prior to erosion. 

Diagram 3. Shows condition after partial erosion but prior to deposition of coastal 
limestones. 

Diagram 4. Shows conditions as they are at present. 

V. GENERAL DESCRIPTION OF ORE DEPOSITS 

Nature of Ore 

The ore mined in the Firmeza district is a mixture, in varying pro¬ 
portions, of magnetite and hematite. The ore is remarkably pure and 
contains little foreign matter. J. P. KimbalP^ gives the following 


figures: 

Per Cent. 

Moisture (in part hygroscopic). 0.24-0.81 

Silica and insoluble. 5.00 -10.50 

Phosphorus. 0.009- 0.065 

Sulphur. 0.045- 0.248 

Iron. 61.00 -68.50 


Although present mining methods make it possible to ship ores somewhat 
lower in iron content, and greater depth in mining has exposed ores some¬ 
what higher in sulphur, the figures Kimball gave in 1884 are substantially 
correct for the ores now being mined. The low phosphorus and the 
absence of appreciable amounts of titanium make the ore a very valuable 
one for the manufacture of high-grade steel. 

Shape and Size of Orebodies 

In shape the deposits are extremely irregular. Whatever their size 
- they show one common feature throughout the area—a far greater ex¬ 
tension in two dimensions than in the third dimension. They resemble a 

J. P. Kimball: Geological Relations and Genesis of the Specular Iron Ores of 
Santiago de Cuba. American Journal of Science, Ser. 3, vol. 28, p. 426 (1884). 









MAX ROESLER 


1809 


series of scattered lenses of irregular outline, that lie in every conceivable 
position. Fig. 12 shows a series of horizontal projections of the ore- 
bodies and a few vertical sections. The projections are drawn to scale, 
and the sections are sketched from exposures in the walls of the mines. 
The outlines represent the boundary of the ore of commercial grade. 
They do not represent the edge of the mineralization. There is gener¬ 
ally a transition from ore to rock, not a definite contact between them. 
This subject will be more fully discussed under the mineralogy of the ore 
deposits. 

The size of the ore deposits varies from pockets containing a few 
tons to lenses whose larger diameters are measured in hundreds of feet 
and whose thickness is from 10 to 50 ft. 


Homonta/ f’rojectiont 
of 

Ore - bodies 



Vertical Secliom 

of 

Ore - Podcei 



Fig. 12. 


Geologic Position 

With the possible exception of the Ocania and Chicharron Mines, the 
ore deposits lie within 200 ft. of the granitic apophyses. These excep¬ 
tions are probably more apparent than real and may indicate that the 
aplite has not yet been exposed, not that it is absent. In most cases the 
ores are directly in contact with aplitic or pegmatitic rock. 

The relation of aplite to ore is exceedingly intimate. In most of the 
mines the ore lies against a floor or wall formed either of aplite or of peg¬ 
matitic granite with much micrographic quartz-plagioclase intergrowth. 
Frequent aplitic dikes traverse the ore, and form prominent features 
because of their light colors, in strong contrast to the black ore and the 
green igneous rocks. In spite of their apparent position as dikes, they 
are not to be considered as later than the mineralization. This will be 
shown in the discussion of the genesis of the ores. 



1810 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


The host rock of the ore is either one of the basic igneous rocks, or lime¬ 
stone. By far the greater part of the ore is in diorite or intrusive diabase; 
some is found in the diabasic extrusive rocks, and only a minor amount 
in the limestones. In at least three of the mines the ore deposits are very 
close to the overlying limestone masses, but there has been no locali¬ 
zation in the limestone, and the larger masses are separated from the 
limestone by basic igneous rock. 

Mineralogy 

The ore minerals are magnetite and specularite, with some amorphous, 
more or less hydrated, hematite in the upper parts of the ore deposits. 
The common gangue minerals are quartz, wollastonite, epidote, and lime- 
iron garnet. The epidote comes in two clearly distinct forms. The 
one is a well-developed, crystalline form, transparent and pleochroic 
from green to yellow. The other is a fibrous and scaly form, lacking in 
well-defined terminations. The well-crystallized form is the one that 



Fig. 13.—Pyrite Crystal from West One Mine. 

is associated with the ores, and other lime silicates. In some of the mines 
calcite is intimately intergrown with the ore. Apatite, titanite, and a 
mineral determined with some doubt as scapolite, were also found in 
rare cases. Secondary calcite, introduced by recent weathering, is 
not uncommon. Pyrite and chalcopyrite are found in most of the mines. 
They are almost always introduced and rarely if ever original constitu¬ 
ents of the ore deposits. The pyrite occurs in well-developed crystals. 
One of these from the West One Mine is shown in Fig. 13. Associated 
with them is chlorite and some sericite. 

Distribution 

The distribution of the minerals appears to be haphazard and 
extremely irregular, but natural phenomena are not haphazard, they 
are logical and sequential. Detailed study has convinced the writer 
that the minerals in these deposits are distributed according to a definite 
order. The most clearly localized material is the massive, fine-grained 





MAX ROESLER 


1811 


intergrowth of magnetite and specularite. This massive ore lies in, and 
close to, fissures, or else directly next to aplitic or pegmatitic granite. 
In the minute intergranular spaces of this ore occur wollastonite and some 
quartz. As the ore becomes less massive toward the margin of the de¬ 
posit the proportion of specularite to magnetite increases, wollastonite 
becomes more abundant, as does quartz, and epidote and garnet appear. 
Still further out from the massive ore, garnet predominates, with 
some epidote, little or no wollastonite, very little quartz, and some more 
coarsely crystallized specularite and magnetite. In some cases this zone is 
composed entirely of massive garnet with very few impurities. Beyond 
the garnet is an area in which epidote and quartz are prevalent. Minerali¬ 
zation of this type is the most widely diffused, and merges gradually 
into partially chloritized and epidotized country rock. The above de¬ 
scription holds only for the typical deposits in igneous rocks. The com¬ 
plete sequence is rarely well-exposed. It can best be observed in the 
East Mine and in West Five Mine. 

Those deposits which are obviously in limestone show two kinds of 
mineral distribution. One is shown in the Chicharron Mine. It is a 
dike-like mass of magnetite and specularite, with interstitial wollastonite. 
The contact with the marble is sharp, and no contact minerals are found. 
The other form of orebody in limestone is a central mass of almost pure 
specularite, in rosette-like clusters, or granular masses, surrounded 
by an intimate intergrowth of quartz well-crystallized calcite, garnet 
and epidote. This form of orebody is best exposed in the North Mine. 
The transition to unaltered marble is not exposed there. In the Ocania 
Mine this transition is exposed and shows a sharp change from garnet 
rock to unaltered marble. 

Apatite is so rare that it is a curiosity in the district. Fig. 14 shows 
a microphotograph of the one section in which it was found in appreciable 
amount. It appears in the usual hexagonal basal, and elongated pris¬ 
matic sections. Later than the apatite in time of crystallization are 
magnetite and the minute garnet-epidote intergrowth. The scarcity of 
apatite and so of phosphorus in the ore is of the greatest economic im¬ 
portance. It is also an indication that phosphorus had little or no share 
in the mineralization. 

The secondary calcite, the kaolin, and the amorphous and hydrated 
hematite, are found either very close to the surface or in channels 
to which meteoric waters have obviously had access. Pyrite is common 
in all the mines and lies close to the surface in an unaltered, well-crystal¬ 
lized condition. 

Interpretation of the Mineralogy 

The first inference to be drawn from the mineralogy of the ore deposits 
is that they were formed at a high temperature. The temperature of 


1812 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


mineral formations is not yet so well known that accurate conclusions 
can be drawn from mineralogy as to the exact temperature at which ore 



Fig. 14.— Specimen from West Five Mine. X 18. Magnetite—black. Epidote 

and garnet—gray. Apatite—clear white. 

deposits were formed, but the occurrence of lime-iron garnet and of 
wollastonite indicates high temperatures. The association with quartzose 
pegmatitic dikes, which, as will appear later, are believed to be con- 



Fig. 15.— Diabase Porphyry, Showing Introduced Quartz and Epidotization. 
From East Mine. X 18. Quartz—white. Epidote—dark. 


temporaneous with the ore formation, places the temperature at from 
575° to SOO^C.^o 


20 F. E. Wright and E. S. Larsen: Quartz as a Geologic Thermometer. American 
Journal of Science, Ser. 4, vol. 27, p, 421 (1909). 








MAX ROESLER 


1813 


The second inference drawn from the mineralogy is that the iron, lime, 
and quartz are either entirely, or in part, introduced material. The 
large quantity and great concentration of the iron oxides makes their 
formation from the rock in which they are found highly improbable, 
and it can be assumed that they represent, almost entirely, introduced 
material. 

The lime silicates, epidote, wollastonite, and garnet are so abundant 
that an addition of lime seems extremely probable. Because the rock, 
now entirely replaced by ore, was a calcic igneous rock, it is impossible to 
determine whether the lime, which was added to form garnet zones, came 
from the magma or from the replaced rock. Since, in places like 
Es^ancia Hill, the garnet zones are out of all proportion to the size of the 
orebodies, an addition of lime from the magma seems probable. The 
major part of the lime is deposited in a zone beyond the iron. In this 
section the lime silicates always show a later crystallization than the iron 
oxides. This makes it appear as if the mineralizing agent deposited most 
of the iron oxides while still able to retain much lime in solution. Further 
evidence of the addition of lime from the magma is afforded by the apa¬ 
tite, intergrown with the magnetite, in the specimen from West Five 
Mine described above (Fig. 14). The epidotization and silicification in 
the outermost zone seems to be largely recrystallization, and represents a 
hydrothermal alteration, more or less in situ, rather than an addition of 
material. The chloritization is also an effect of this hydrothermal 
metamorphism. Six samples of diabase showing more or less epidote were 
analyzed for lime. They were selected at various distances from a lime¬ 
stone inclusion, in order to show a supposed absorption of lime. The 
variation in the lime content is so slight that no addition of lime in this 
zone can be postulated. The quartz is probably largely a byproduct of 
the alteration of hornblende to epidote. It is also in part introduced, 
as is shown in the microphotograph of a specimen from the diabasic 
porphyry in the East Mine (Fig. 15). 

In regard to the chemical form of the mineralization, inferences are 
largely negative. Evidence of the participation in the mineralization of 
any of the halogens is practically lacking. The apatite and dubious 
scapolite indicate some chlorine, but the occurrence of chlorine-bearing 
minerals is so rare that the introduction of the iron as chloride cannot be 
shown. CO 2 would be expected to show its presence in the formation 
of carbonates in the zone of hydrothermal alteration. No appreciable 
amount of carbonates was found, except in the occurrences in limestone. 
The presence of much water is shown, however, by the extensive hydro- 
thermal alteration in the outer zone of mineralization. If the inferences in 
regard to the temperature of the formation of the ore deposits is correct, 
it is more than 200° above the critical temperature of water (358°C.). 
The fact that this water carried material in solution makes it impossible 


1814 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


to prove that it was in the form of vapor; but the high temperature and 
the fact that the mineralizers were able to permeate dense rocks so readily 
makes it probable that they were in the gaseous rather than the liquid 
phase. The mineralizers are, therefore, believed to have been domi¬ 
nantly water vapor, carrying with it iron, lime and silica. The variation 
in mineralization with decreasing intensity is believed to be as shown in 
the diagram. Fig. 16. 

A later mineralization is represented by the pyrite and chalcopyrite. 
Field observation shows that the pyrite in the ore lies in channels along 
which solutions have passed. In the ore it is usually accompanied by 
chlorite. Where the pyritization has taken place in the wall rocks, as 
at the west side of the Ocania Mine, both chlorite and sericite occur. The 
pyrite seems to represent a very much later stage of mineralization than 
the magnetite and hematite. It is impossible to prove any definite 

Ml N E R A L IZ ATIDN DIAGRAM 

Siaft •/ AccttSitn t/Mat€r-iQ.i Siu^t v/ A/tri-ation cf /iattfiat 


Hyd>-ot/t«frrta.l Stay* Qu».rt^ ■ . ■ > 

—« • Sfi4,tiot€ . . - > 

< ' C A{»fit€ -• 

> ' " t ^ __ % 

Fig. 16. 

connection between the pyritization and the mineralization that produced 
the orebodies. It seems probable that the solutions that brought the 
pyrite came in at the time of the intrusion of the later dikes. 

Superficial Alteration 

W. Lindgren believes that the hematite is the result of the alteration of 
magnetite by surface agencies. He says: 

‘‘-the hematitization is probably a low-temperature process developing 

gradually under the influence of oxidizing atmospheric waters. ”21 

The occurrences in the Firmeza district are in entire accord with those 

21 W. Lindgren and G. P. Ross: The Iron Deposits of Daiquiri, Cuba. Trans, 
vlo. 53, p. 52 (1916). 


S ftc»/arite 
y>/c/iasto^it€ 




"Pr i.friary Qvartz 


























MAX ROESLER 


1815 


recorded by Lindgren at Daiquiri. There is an increase of hematite in 
the higher levels of the mines. A polished specimen of the massive ore 
from the Chicharron Mine shows very clearly the intimate intergrowth 
of specularite and magnetite, and some of the specularite forms a later 
veinlet through the magnetite; but to accept without question specu¬ 
larite as an oxidation product of magnetite is difficult. The writer has 
been unable to find any record of the synthesis of specularite except at 
high temperatures, or of the occurrence of specularite as the result of 
surface oxidation except under superimposed regional metamorphism. 
It is not the crystalline facies of hematite that forms under surface 
agencies, as the result of dehydration of limonite, in the ores of Mayari. 
Lindgren does not state that the process of hematitization produces the 
crystalline facies of hematite (specularite). But since it is the crystalline 
phase that is abundant, and the earthy phase rare, it must be the specu¬ 
larite to which he refers. He does say:22 

“The pits in the hematite are probably caused by the local development of a 
softer or earthy facies of the mineral.” 

In spite of the fact that all the observations accord with the theory 
advanced by Lindgren, the writer desires to suggest another hypothesis— 
that is, that both the magnetitization and the hematitization are due to a 
primary mineralization by gaseous solutions deficient in ferrous oxide. 

F. W. Clarke says:^^ 

“Ferric oxide can crystallize out as hematite only when ferrous compounds are 
either absent or present in quite subordinate amounts, for ferrous oxide unites with it 
to form magnetite.” 

The crystallization of specularite as a later phase, from a gaseous solution 
containing insufficient ferrous oxide to produce all magnetite, is in accord 
with Clarke’s observation. Deficiency of FeO could account for a change 
from magnetite to specularite about centers of crystallization. It could 
also account for a diffusion of the hematitization to a higher level, further 
from the centers of mineralization than the magnetitization. Local varia¬ 
tions in the mineralizing solutions account for the variations in the pro¬ 
portion of hematite to magnetite in bodies equally close to the parent 
magma. 

The only important effect ascribed to surface waters by the writer is 
the oxidation of the pyrite near the surface, and the resulting decrease in 
the undesirable sulphur content. 


22 Op. ciL, p. 52. 

23 F. W. Clarke: Data of Geochemistry. Bulletin No. 610, U. S. Geological 
Survey, p. 347. 




181G 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


VI. GENESIS OF THE ORE DEPOSITS 
Previous Theories 

The preceding description of the ore deposits, and discussion of their 
mineralogy, makes it possible to consider the larger features of their 
mode of formation. As this is purely a matter of interpretation, it is 
necessary to consider first the interpretation given by others. J. P. 
Kimball, writing in 1884-85, and F. F. Chisholm, in 1890, formed their 
conclusions from observations made in the Firmeza district. A. C. 
Spencer based his theories on work done at both Firmeza and Daiquiri 
in 1901. The papers by J. F. Kemp, and by W. Lindgren and C. P. 
Ross, were written more largely from evidence gathered at Daiquiri, 
with some specimens and a brief visit by Kemp to the Juragua mines in 
1914. J. T. Singewald and B. LeRoy Miller made a brief visit to the 
Firmeza and Daiquiri districts in the fall of 1915. 

J. P. KimbalP"^ recognizes two types of ore deposit in the Juragua dis¬ 
trict. These are “replacements’’ of the coral limestone by iron-bearing 
solutions, and “concentrations” of ferric oxide in the diorite, “almost 
in situ” Both replacement and concentration are ascribed to the 
action of circulating meteoric waters. 

F. F. Chisholm^^ discusses the theory advanced by J. P. Kimball, and 
disagrees with it. He states his own opinion as follows 

“My conclusions, after going in detail over most of the exposure made by the 
Union cut, were that, whatever the exact character of the ore deposit, the present 
position of the ore cannot properly be considered the result of local metamorphism of 
limestones by the action of surface waters containing iron leached from the overlying 
mass of iron-bearing diorite. I am much more strongly inclined to consider the ore 
here either the result of concentration within a diorite dyke which was originally 
characterized by the presence of a large percentage of iron, or else a distinct band form¬ 
ing a portion of a larger dyke. In other words, I am strongly of the opinion that the 
source of the ore is from below, and consequently that the loyalty of these deposits 
may be relied on below the limits of atmospheric action. I regret that I was unable 
to go into the question in detail, and get positive facts in support of my belief, but 
that I am obliged to admit that my examination was too superficial to enable me to 
prove my views.” 

A. C. Spencer,after considering several possible explanations of the 
genesis of the ore deposits, comes to the conclusion that they are parts of 

24 J. P. Kimball; Geological Relations and Genesis of the Specular Iron Ores of 
Santiago de Cuba. American Journal of Sciences, Ser. 3, vol. 28, p. 426 (1884). 

The Iron-Ore Range of the Santiago District of Cuba. Trans., vol. 13., pp. 613- 
634 (1884-85). 

25 F. F. Chisholm: Iron-Ore Beds at the Province of Santiago, Cuba. Proceed¬ 
ings of the Colorado Scientific Society, vol. 3, part 3, pp. 259-263 (1888). 

28 Op. cit., p. 262. 

27 C. W. Hayes, T. W. Vaughan, and A. C. Spencer: Report on a Geological Re¬ 
connaissance of Cuba, 1901. 







MAX ROESLER 


1817 


an older limestone-schist series which has been completely involved in the 
later igneous intrusions. The following quotation shows how completely 
Spencer supposed this older series to have been immersed in the igneous 
rock.2^ 

“A mass of many million tons weight floated upward by the buoyant effect of 
molten rock in motion from the interior toward the surface of the earth, is the only 
conception which adequately accounts for the mode of occurrence of the orebodies 
of the Magdalena and the Lola Mines at Daiquiri; while, though less strikingly shown, 
at Firmeza it is likely that the masses of schist, marble and ore have been likewise 
actually suspended in the molten lava.” 

J. F. Kemp^® divides the orebodies into two types—the “Distinctive 
Contact Zones’^ in limestone, and the orebodies in the diorite. The 
former he regards as due to contact-metamorphic effects produced in the 
limestones by the granite. Of the orebodies in the diorite he says: 

“One is led to the conclusion that while the diorite mass was still hot in the depths 
or after it had consolidated and had been penetrated by some other and still hot 
intrusive in depth, a pronounced northwest and southeast fissured zone was formed, 
up through which came the emissions, fluid or gaseous, which brought the iron for 
the ore, the pyrite, the garnet and the epidote; the sulphur for the pyrite; and the silica 
for the quartz, the garnet and the epidote. The lime required by the garnet and the 
epidote may have been derived from the plagioclase and hornblende of the diorite, or 
srom included blocks of limestone, or deep-lying limestone, or from several of these 
fources.” 

Another quotation from the same article might indicate that Kemp 

suspected what has become the conviction of the writer:^® 

* 

“One cannot help associating the granitic or pegmatitic dikes with some large 
parent body. The natural one is the intrusive granite mentioned at the outset. 
Yet this granite has produced contact zones on the older limestone with orebodies, 
whereas the granitic and quartz-porphyry dikes are, in two cases at least, later than 
the large orebodies. We can only suspect the possible connection without being able 
to prove it.” 

Kemp apparently bases his conclusion that the aplite dikes represent a 
later intrusion into the ore on the fact that the dikes appear to cut the ore. 
That another hypothesis is possible will be shown later. 

W. Lindgren and C. P. Ross,^^ on evidence gathered by the senior 

author, deduced the following conclusions 

“From the above it is clear that the primary iron oxide of the deposits at Dai¬ 
quiri is a magnetite, which subsequently has been altered more or less completely to a 

28 Op. cU., p. 82. 

2® J. F. Kemp: The Geology of the Iron-Ore Deposits In and Near Daiquiri, Cuba. 
Trans., vol. 53, p. 30 (1916). 

80 Op. cit., p. 21. 

31 W. Lindgren and C. P. Ross: The Iron Deposits of Daiquiri, Cuba. Trans., 
vol. 53, p. 52 (1916). 

32 Op. cit., p. 53. 





1818 


IRON-ORE DEPOSITS OF THE -FIRMEZA DISTRICT 


hematite. The discussion of genesis may therefore be divided into two parts: the first 
relating to the origin of the magnetite; the second to its subsequent hematitization. 

The mineral association of the magnetite, particularly the presence of much 
garnet, shows that it originated under high-temperature conditions. 

On the other hand, the hematitization is probably a low-temperature process 
developing gradually under the influence of oxidizing atmospheric waters.” 

The problem of hematitization has already been discussed. 

Further on three theories discussed* by A. C. Spencer are rediscussed 
by the authors. After dismissing the other two theories, the second 
theory is accepted, as follows: 

“There remains the second theory, accounting for the large masses of magnetite 
included in the diorite by contact-metamorphic limestone, by which the latter has 
become almost entirely replaced by magnetite derived from magmatic emanations 
rich in iron. While it is freely admitted that the genesis of the Daiquiri deposits is 
difficult to explain, it will be shown that the view outlined in the previous sentence 
has much in its favor.” 

J. T. Singewald and B. LeRoy Miller discuss the theories advanced 
by J. F. Kemp, and by W. Lindgren and C. P. Ross in the papers 
cited above and come to the conclusions summed up in the following 

paragraph: 33 

“To sum up our opinions, the Cuban iron ores are contact-metamorphic deposits 
localized about engulfed blocks of limestone in diorite. In such cases, where there 
was a limited supply of magmatic emissions, there resulted the contact metamorphism 
of only a part of the limestone block. Where the supply was ample and the action 
most intense, not only was the block of limestone completely replaced, but complete 
endomorphism of the igneous rock on a large scale occurred in the vicinity.” 

The above are the interpretations offered by others who have studied 
the field more or less closely. But a study of different exposures and a 
different viewpoint, have led the writer to conclusions which are somewhat 
at variance with those quoted. 

Hypothesis of the Genesis of the Ore Deposits 

Any comprehensive theory concerning the formation of an ore deposit 
in a rock of which it is not an original part— i.e., an epigenetic deposit— 
must account for four things: 

I. The source of the material forming the deposit. 

II. The vehicle that introduced the material. 

III. The channel through which the material was introduced. 

IV. The cause for the deposition of the material. 

Source of the Iron Ore 

The ultimate source of the iron ore was the diabasic magma. The 
extruded part of this magma, with the involved limestones, together with 

33 J. T. Singewald and B. LeRoy Miller: The Genesis and Relations of the Dai¬ 
quiri and Firmeza Iron-Ore Deposits, Cuba. Trans., vol. 53, p. 73 (1916). 




lVtA.X ROESLER 


1819 


the chilled upper part of the magma (the diabases and diorite) form the 
host rock of the ore deposits. It has already been shown, in the discus¬ 
sion Cf the areal geology of the district, that this magma was differen¬ 
tiated, that the earlier igneous rocks represent the parent magma and its 
early differentiation products, and that the latest rock differentiate was 
the granite massif with its aplitic apophyses. These aplites, which are, 
under anhydrous conditions, extremely viscous, must have contained large 
quantities of crystallizers, to keep them fluid and enable them to pene¬ 
trate the basic rocks as sills and dikes. It is believed that these crys¬ 
tallizers were mostly composed of 'water vapor well above the critical 
temperature, and that they held in an ionized state the ore minerals. 

V 

Vehicle to Carry the Material 

These concentrated crystallizers were also the vehicle to carry the 
mineral burden into the rocks which act as host for the ore deposits, i.e., 
the crystallizers plus the minerals are the mineralizers. Their nature has 
already been discussed under the interpretation of the mineralogy. 

Channels through which the Materials Were Introduced 

One of the striking features of the larger Firmeza deposits is that > 
the ores have almost obviously avoided the masses of marmorized lime¬ 
stone. This can be explained by the fact that the channels, through 
which the mineralizers entered, were not lines of weakness or shear zones 
produced by structural faulting, but were cooling cracks in the igneous 
rocks. 

Causes of Deposition 

The causes of deposition may be of either a chemical or physical 
nature, or a combination of the two. It has been the tendency of 
geologists to ascribe to chemical action the dominant role in contact- 
metamorphic actions. This makes it difficult to account for ore deposits 
in two rocks as chemically different as diabasic igneous rock and marmor¬ 
ized limestone, except by postulating different theories. If it is believed 
that the dominating cause of deposition is physical, and is inherent in 
the mineralizing solutions, whether liquid or gaseous, this difficulty is 
obviated. It is the writer’s opinion that such was the case in the forma¬ 
tion of these deposits. The mineralizers were under such great pressure 
and at such high temperature that they had the power to diffuse through, 
and either partially or wholly absorb, any rock with which they came 
into contact. This diffusion and partial absorption would rob the mineral¬ 
izers of a large part of their activity, and would cause deposition of the 
minerals in a definite order. The order would be dependent on the 


1820 


lUON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


saturation of the gases or solutions with the material to be deposited. 
The field evidence for such an order is clear, and as shown in discussing 
the mineralogy of the deposits, magnetite and specularite are the first 
minerals deposited. As a result, the magnetite and specularite are local¬ 
ized in and near the fissures through which the solutions had access, while 
the epidote, which is probably only in part due to accession of material 
from the magma, and is more largely a recrystallization of material 
present in the host rock, is much more widely diffused. Joseph Barrell, 
in conversation with the writer, suggested that such a hypothesis may also 
account for the association of aplitic and pegmatitic dikes with basic 
mineral segregations. The dikes are regarded as the residual, acidic 
rock material left in fissures, from which the mineralizers had gone into 
the rockbody, and in the process had effected a separation of acidic and 
basic material. 

Under the hypothesis advanced, the orebodies owe their localization 
in igneous rock or limestone almost entirely to the accessibility of the rocks 
to the mineralizing solutions. The same causes govern all the cases. 

Briefly stated, it is the writer’s belief that the orebodies in the Firmeza 
district are due to mineralizers concentrated by further differentiation 
from the granitic massif, which is itself a differentiate of the diabasic 
magma. These mineralizers diffused from the igneous-rock material 
into those rocks to which fissures gave access, and, in diffusing, deposited 
their mineral burden, and left the rock material with which they had 
been mixed in the fissures, as aplites and pegmatites. 

Under this hypothesis the mineralization becomes a definite event in 
the igneous cycle, which cycle may be restated as follows: 

1. Extrusion of diabasic rock material. 

2. Intrusion of diabasic magma. 

3. Formation by differentiation of more acidic residual liquid in 
magma reservoir, with concentration of mineralizers. 

4. Batholythic invasion of granitic material, together with minerali¬ 
zers. 

5. Further differentiation of the granitic batholith and escape of 
mineralizers with some acidic rock material, into cooling cracks in country 
rock. 

6. Separation of basic mineralizers, and acidic rock material, with 
contemporaneous formation of ore deposits and aplitic dikes and pegma¬ 
titic apophyses. 

The hypothesis submitted above is given prior to a detailed descrip¬ 
tion of the ore deposits. It must be tested by its application to the 
phenomena observed in the field, and by its ability to meet the objections 
raised by other writers on the same subject. 


MAX ROESLER 


1821 


Discussion of the Different Hypotheses 

The hypotheses of the different geologists who have visited the region 
have been given, either as abstracts or by quotations. The earliest of 
these, that by J. P. Kimball, does not account for the formation of what 
are now known to be high-temperature minerals: garnet, wollastonite, 
etc. Kimball recognized, however, that some of the ores lay in diorite 
and could not be accounted for by a hypothesis which depended entirely 
on limestone as a precipitant. F. F. Chisholm does not attempt to formu¬ 
late a complete theory of the genesis of the ore deposits. With his con¬ 
clusion that the mineralizing solutions came from below, and were not of 
meteoric origin, the writer entirely agrees. 

The theory accepted by A. Spencer requires an older limestone-schist 
series. Limestone was found in the Firmeza district in considerable 
abundance, but schist could not be found by the writer. The occurrence 
of tuff-limestones interbedded with the volcanic extrusive material makes 
it seem probable that the period of sedimentation, and the initiation of 
the igneous cycle, were not separated by a time interval sufficient for 
the forming of surface orebodies and their entombing in igneous rock. 
This theory also fails to account for the forming of ore in diorite. In a 
tunnel under West Five Mine the transition from fresh diorite to granular 
magnetite can be traced. The transition is gradual and there is no con¬ 
tact which could possibly be interpreted as the margin of a partly assimi¬ 
lated block. 

Later writers all agree in ascribing an igneous origin to the mineraliz¬ 
ing solutions. The principal divergence is in the amount of influence 
ascribed to the limestone. Lindgren and Ross believe the ore to be defi¬ 
nitely localized in limestone. Singewald and Miller regard the ore as in, 
and about limestone. Kemp believes that some of the deposits are 
independent of limestone. In regard to this feature the writer agrees 
entirely with Kemp. The conception of the orebodies as metamorphosed, 
engulfed limestone masses is difficult. The shape and position of the ore- 
masses demand that the entombed blocks should have been comparatively 
thin, and that they should have come to rest in every conceivable position. 
This theory completely fails to account for the gradual transition from 
ore to diorite shown at its best in West Five Mine. Such a deposit 
could be accounted for only on the basis of complete assimilation of the 
limestone, and a deposition of magnetite about the locus of assimilation. 
Any theory that places the burden of producing the orebodies upon the 
diorite, is open to one great objection. It demands that a magma of 
almost gabbroic basicity shall have produced contact-metamorphic 
phenomena of the most intense variety. Kemp recognized this, and 
ascribes the orebodies in limestone to the granite, and the orebodies in 
the diorite to solutions from “some other” intrusive. But Lindgren and 
8 


1822 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


Ross, and Singewald and Miller regard the diorite as the source and as 
the cause of the mineralization. Another objection is the fact that, 
under that theory, the diorite must have exercised a strong selective 
tendency. Unaltered marble within 20 ft. of massive ore, and separated 
from the ore by recognizable diorite, can be seen at West Four. Such a 
case is not rare, it is a common feature. In one of the old cuts above 
West One Mine there is exposed a small block of marble, completely 
surrounded by diabase containing small ore masses. But the marble 
is entirely unaffected. Contact-metamorphic phenomena are undoubt¬ 
edly capricious, but if another explanation will solve the problem in 
such a way as to show that the capriciousness is more apparent than 
real, it must at least be considered. 

The great objection to ascribing the source of the ores to the granitic 
batholith lies in the interpretation of the aplitic and pegmatitic dikes. 
Field observation clearly establishes the direct connection between these 
rock types and the granitic massif. If these most acidic facies represent 
a later intrusion into the ore, the ore cannot come from the granite. 
Kemp believes they are later. He says:^'^ 

“-whereas the granitic and quartz-porphyry dikes are, in two cases at least, 

later than the large orebodies.” 

Lindgren and Ross^® agree with this. 

“The dikes of igneous rock^^ intruded into the iron ore appear to be somewhat 
different from the diorite and are either granite porphyry or aplite; that is, comple¬ 
mentary dikes of a later generation.” 

F. Klockmann, writing on contact-metamorphic magnetite deposits in 
general, puts the matter even more strongly 

“Wiederholt wird angegeben, dass aplitische Gange und Granitapophysen die 
Magnetitlager statte durchsetzen. Gibt es denn fur den Unbefangenen dafiir noch 
andere Deutung als die, dass der Granit in eine von ihm vorgefundene Lagerstatte eine 
Apophysen entsendet hat?” 

As a general proposition, the very fact that aplitic dikes and granite 
apophyses are repeatedly reported as traversing magnetite deposits is 
the strongest possible argument against the purely fortuitous intrusive 
nature of such apophyses. It was this constant relationship observed 
in the field study, that first convinced the writer that there must be 
definite connection between the forming of the orebodies and of the 
granitic apophyses. 

J. H. L. Vogt recognizes a connection between the granite and its 
apophyses, and the magnetite deposits of Kristiania. He says:^^ 

Op. cit., p. 21. 

Op. cit., p. 54. 

36 F. Klockmann: Uber Kontaktmetamorphe Magnetitlagerstatten. Zeilschrift 
fur Praktische Geologic, vol. 12, p. 81 (1904). 

37 J. H. L. Vogt: Problems in the Geology of Ore Deposits. Trans., vol. 31 p 
138 (1901). 







MAX ROESLER 


1823 


“A study of the Kristiania contact-deposits indicates that the formation of the 
ores preceded the solidification of the granitic magma. Even when the ores occur 
in slates immediately adjacent to the granite, or in the small Silurian fragments 
completely surrounded by granite, they are never found also in the granite itself. 
This is to be simply explained by the supposition that from the still liquid magma the 
ores were ‘blown into’ the adjoining rigid rocks. —The presence in these deposits 
of granitic apophyses, already mentioned, is another proof that they were formed 
before the solidification of the granite.” 

He regards the occurrence of the apophyses with the ore in the Kristiania 
district as proof that the granitic magma had not yet solidified. 

The absence of ilmenite in the Firmeza occurrence is also an indication 
of their intimate connection with the granitic magma. Vogt has given 
some very complete studies of the relationship between the different 



Fig. 17.—Aplitic Granite Bordered by Magnetite and Epidote. Tunnel 
AT Elevation op 299 Ft. under West Five Workings. Magnetite Caught in 
Aplite = M. Actual Size. Aplite—white. Magnetite—dark. 

magnetite deposits and their sources. A quotation that shows some of 
his conclusions follows 

“Die Erfahrung ergiebt, dass bei der ‘oxydischen’ Erzaussonderung es namentlich 
das ‘Eisenoxyd-mineral’—bei den Gabbros Titaneisen oder Titanomagnetit, bei den 
Peridotiten Chromit—ist, welches concentrirt wird. Es ist somit a priori anzunehmen, 
dass etwaige ‘oxydische’ Erzausscheidungen in den Graniten einen ahnlichen nie- 
drigen TiOz-Gehalt fiihren miissen wie die in dem Granit normal ausgeschiedenen 
(wohl namentlich Magnetit und Eisenglanz, untergeordnet Titaneisen.) ” 

The stronge^ evidence of the intimate relation between the 
granitic apophyses and the mineralization is based on field observation. 
Some of the small dikes are reproductions in miniature of the larger 
occurrences. Figs. 17, 18 and 19 are photographs of two of these small 
dikes. 

Fig. 17 is of a specimen from the ore in the tunnel under West Five 

38 J. H. L. Vogt: Zur Classification der Erzvorkommen. Zeilschrift fur Praklische 
Geologie, vol. 2, p. 394 (October, 1894). 



1824 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


Mine. This is as deep-seated an ore deposit as has been exposed, and is 
the one most clearly independent of limestone. It is noticeable how 
entirely clear-cut is the contact between aplite and magnetite in the 
lower part of the picture. At the same time the other contact is less 
sharply defined and clearly shows some magnetite trapped in the aplite. 



Fig. 18. —Photograph of Specimen from East Mine, Showing Rim of Gar¬ 
nets Developed between Aplitic Granite (White) and Diabase Porphyry 
(Dark). Actual Size. 


Fig. 18 is a photograph and Fig. 19 a microphotograph of a specimen 
from the East Mine. This specimen comes from the area of diabasic 
rocks, that lies between the ore in the East Mine and the ore in the pit 
above, known as North Mine. The specimen shows garnet, merging 



Fig. 19. —Garnet Band between Aplitic Granite (Lower Right) and Diabase 
Porphyry (Upper Left). From East Mine. X 18. 


on one side into diabase porphyry, on the other into aplite. The writer 
can see only one explanation for this specimen, and that is a change in 
the mineralizing solutions from intermixed mineralizers and acidic rock 
material to aplite. 

It is on the basis of such occurrences, and for the reasons given, that 




MAX ROESLER 


1825 


the writer believes: that the aplite and ore are phenomena produced at 
approximately the same time; that both were formed from a mixture of 
mineralizers and rock material derived from the granitic magma; and 
that the iron oxides, lime and the major part of the silica, held in aqueous 
solutions above the critical temperature, diffused into the wall rock, 
leaving the residual rock material in the fissures as aplitic dikes. 


VII. DETAILED DESCRIPTION OF THE ORE DEPOSITS 

In order to test the hypothesis stated above in regard to the genesis 
of the ore* deposits, it must be applied to the different occurrences of ore 
in the district. To do this, a detailed description of the more carefully 
studied mines will be given, and the mode of formation of the orebodies 
discussed. 

OcANiA Mine 

The Ocania is the most westerly of the Juragua Iron Co.’s mines. 
It lies on a steep hillside, at an elevation of from 860 to 1,085 ft. 



jtjq 20. —Specimen from Ocania Mine, Level 2. The Dark Material is 
Garnet. The Light Material is Wollastonite. The Structure is Attrib¬ 
uted TO Diffusion. Actual Size. 

The wall rocks are coarse, diabase porphyry, volcanic agglomerates, 
and marble. The contact between the granitic and diabasic rocks lies 
on the south slope of the hill, at an elevation of about 700 ft. A quartz¬ 
bearing, andesitic dike is found in the mine itself. The ore forms a series 
of lenses that strike in a northwesterly direction, and have a steeply 
inclined dip to the southwest. These lenses are made up almost entirely 
of hematite and quartz, with little or no magnetite. There is considerable 
pyrite through the ore in various places, and, at the edge of the lime¬ 
stone, chalcopyrite and manganese oxide are found. Some fragments 
of diabase, with native copper in them, were observed near the limestone. 
Between the ore and the limestone are masses of garnet rock. Near the 
bottom of the oreliody, as exposed on the southeast side of the mine, was 


1826 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


found a rock (Fig. 20) which shows, in part, alternating layers of brown 
garnet, and a greenish mineral which the microscope shows to be wollas- 
tonite. As the accompanying microphotograph (Fig. 21) of the contact 
between the garnet and wollastonite shows, the two bands have an inter¬ 
locking structure, perpendicular to the boundary. The black crystals 
in the wollastonite band are magnetite. The garnet does not show crystal 
edges. Toward the center it is very dusty, with undeterminable inclu¬ 
sions. The wollastonite forms an aggregate of poorly developed, pris¬ 
matic crystals. A somewhat similar structure, made up of magnetite 
and actinolite, is shown in a specimen from the Juragua Mines described 
by W. Lindgren. He says: 

“The texture of this specimen strongly suggests diffusion banding, such as might 
form in a material, a limestone perhaps, freely penetrated by hot iron-bearing solution.” 



Fig. 21.—Contact between Garnet and Wollastonite in Rock Showing 
Diffusion Structure. From Ocania Mine. X 18. Magnetite—^black. Garnet 
—dark. Wollastonite—grey. Holes in thin section—white. 

In the case of the Ocania specimen the solutions were probably lime-bear¬ 
ing and lower in iron. Whether the original rock was limestone or dia¬ 
base porphyry, it is not possible to tell. It is true of this mine that the 
mineralization effects have spread further into the diabasic rocks than 
into the marble. The clean white marble is separated from the ore by 
only a few feet of garnet rock, while the diabase is garnetized, near the 
ore, and epidotized for tens of feet from the ore. The ore itself is so 
complete an alteration of whatever wall rock it replaces that there is no 
prima facie evidence of what it originally was. The pyritization is later 
than the principal period of ore deposition, the pyrite forming in frac¬ 
tures and cavities in the ore. The chalcopyrite accompanies the pyrite. 

Surface action, producing partial hydration of the ore and consider¬ 
able infiltration of secondary calcite, obscures the evidence. 


MAX ROESLER 


1827 


Northeast of the mine workings is the largest exposure of marble found 
in the district. It is cut by sills of an entirely epidotized, basic, igneous 
rock. It is separated from the orebodies by massive garnet rock, or 
highly garnetized and silicified diabasic rock. The map (Fig. 22) shows 
the relation of orebodies to wall rock. The commercial ore is sharply 
bounded, but the mineralization is not. 

The striking features in this mine are the absence of magnetite and 
of highly acid wall rocks, and the clear evidence that the diabasic rocks 
are more diffusely mineralized than the marble. At the same time the 
resemblance of the blocks of ore to engulfed limestone blocks or to roof 
pendants, is noticeable. 

If the Ocania Mine were the only one studied, it would be difficult for 
the writer to defend his hypothesis. There are no aplitic or pegmatitic 



□ C AN I A M rNE 

Fig. 22. 


rocks in evidence. Except for one dike of doubtful age, no quartz-bear¬ 
ing Igneous rock is exposed in the mine. There is abundant limestone. 

There are also some features that are not explained by any theory 
involving the diabase as the ore-bringing rock. The diffuse mineraliza¬ 
tion of the diabasic porphyry indicates a hydrothermal effect, later than 
the consolidation of the diabase. It is difficult to ascribe to the diabase 
porphyry a hematitizing effect on included limestone, or even a mag- 
netitization free of chrome or titanium minerals, with a superimposed 
hematitization. The fact that the larger part of the marble has suffered 
no mineralization is also unexplained by any theory that makes the over¬ 
whelming of the limestone by the diabase the cause of mineralization. 

On the other hand, if the solutions are supposed to come from the 
granite, the difficulties of explanation are not so great. A fissure in the 
diabase near the limestone, localized the ore and the mineralization in 

























1828 


IRON-OKE DEPOSITS OF THE FIRMEZA DISTRICT 


both formations. The distance of the ore exposed from the parent magma 
accounts for the preponderance of hematite over magnetite. 

West Five Mine 

This mine is the furthest west of the mines in the vicinity of Firmeza, 
and lies at an elevation of from 420 to 718 ft. There is a tunnel under the 
mine at a level of 299 ft. 

The ore lies in flat or in steeply inclined lenses. It is almost entirely 
magnetite, the enclosing wall rock diorite, with considerable, more or 
less aplitic, granite through and near the ore. The diorite varies from 



Fig. 23. 

the even, granular type shown in Fig. 8 to a porphyritic type. No 
fragmental diabasic rocks occur, nor is there any trace of limestone. 

The rocks from the aplitic dike, in the west side of the mine, were 
described under the granitic rocks. The connection between aplite 
and ore is shown on a small scale in the photograph (Fig. 17) of a small 
dike of aplite from the tunnel under the mine. The magnetite and epi- 
dote lying immediately next to the aplite, merge gradually into the 
granular diorite. There can be no question of any rocks being involved 
other than the diorite and the aplite. Their inter-relationship has been 
discussed in considering the question of genesis. Considerable garnet 
is found in the mine workings, and its occurrence is similar to the mag¬ 
netite and epidote. In one small exposure the position of the garnet, as 
a contact effect in the diorite, next to the granite, is clearly shown. This 











MAX ROESLER 


1829 


is on the north side of the bottom level. The epidotization and silicifica- 
tion are more widely diffused from the granite than are the magnetite 
and garnet. One specimen, from the lowest level, showed an inter¬ 
growth of apatite with magnetite, and garnet and epidote, cut by later 
veinlets of epidote (Fig. 14). This is the only case in which apatite 
amounted to more than a very minor accessory. 

On the south side of the mine is an east-west fault steeply inclined to 
the north. It is obviously post-mineral, and appears not to be of very 
great throw.. 

Summing up the evidence from this mine we find: no limestone; 
much aplitic or porphyritic granite; almost no specularite; but much 
magnetite, garnet, epidote, quartz—all in diorite. 

The ore deposits of this mine offer the clearest evidence that lime¬ 
stone could not have been the dominant cause determining the locus of 
their deposition. There is no limestone in the immediate vicinity. The 
transition from ore to diorite is gradual. The mineralogy shows none of 
the well-crystallized calcite that is so abundant in the ore deposits that 
were obviously formed in limestone. 

The intimate relation between ore and aplite is also well shown 
here. The dike exposed in the west side of the workings has led other 
observers to believe the granitic apophyses later than the ore, but as 
shown under the discussion of the various theories, the same phenomena 
are interpreted by the writer to indicate the contemporaneous formation 
of the ore and the aplite. 

All the phenomena can be explained on the hypothesis advanced. 
That is that the aplite, the magnetite, and the lime silicates are all the 
effect of the one mineralizing period. 

Loma Alta Mine 

The Loma Alta workings lie at the top of a hill, just east of West 
Five Mine. They are at an elevation of from 900 to 1,000 ft. As they 
have been practically abandoned for some time, weathering agencies 
have obscured much of the evidence. Cropping out on the east side and 
pitching under the workings at a flat angle, is a sheet-like mass of 
porphyritic, pegmatitic granite. In the southwest corner of the workings 
is recognizable diabase porphyry. What is left of the ore is earthy hema¬ 
tite lying on the granite with some kaolin and chlorite. All around the 
workings on the hill are rounded boulders of more or less pure magnetite. 
The association of the granite, diabase and ore in this mine is suggestive, 
but the evidence is too obscured to be conclusive. The earthy hematite 
undoubtedly owes its origin to the weathering of the primary, crystal¬ 
line iron oxides. There is no reason to believe that the process did not 
involve the formation of limonite and its dehydration. 


1830 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


West Three Mine 

An exposure in this mine, which lies on the same hill, south of and 
below Loma Alta Mine, is worth describing. It is a mass of magne¬ 
tite, in diabase, directly next to a vertical pegmatitic granite dike. The 
rocks are all fairly unaltered, and the contact relationship well shown. 
There is no reason to suspect that any limestone was involved. 

West Four Mine 

This mine is located northeast of Loma Alta, at an elevation of from 
645 to 935 ft. At the north end of the mine, in the upper levels, is a mass 
of clear white marble, entirely unmineralized. The wall rock in the upper 
levels is diabase porphyry; in the lower levels it is diorite. The diabase 
and diorite are both cut by somewhat porphyritic and pegmatitic granite. 
The ore is magnetite, and hematite and magnetite, and lies in lenses; 
whose major axes vary from a vertical to a horizontal position, on top 
of and next to the granite. These lenses occur mostly in the diorite, 
partly in the diabase, but not, so far as exposed, in contact with the 
marble. The entire series, diabase, diorite, granite, ore, is cut by a large 
dioritic dike. The mineralization effects are no different from those in 
West Five Mine. The chief difference is that there is marble exposed 
in the West Four workings. So far as can be determined it has had no 
direct effect on the formation of the ore deposits. 

West One Mine 

The West One workings are located north of Firmeza along the rail¬ 
road tract. Exposed for a long time and not much worked of late years, 
they offer a poor field for study. Altered diabase and diorite, highly 
mineralized, are the wall rocks. Neither limestones nor granite are in 
evidence. From one of the cuts that is being worked, come the well- 
developed pyrite crystals, of which one is shown in Fig. 13. This 
exposure shows the pyrite all through the magnetite in cavities and along 
minute fractures. It establishes the age of the pyritization as definitely 
post-magnetitization. 

Fig. 24 is a photograph of a drawing made with a camera lucida, 
from a thin section of a rock from West One Mine. The specimen is 
dark and dense, and shows patches of magnetite. In thin section the 
rock proves to be a diabasic porphyry, partly replaced by magnetite. 
The replacement is apparently independent of the mineralogy of the 
replaced rock. The magnetite occurs in patches in the groundmass, or 
in the phenocrysts, or partly in each. 

West One Mine offers no new evidence in regard to the genetic problem. 
It does offer, however, an excellent field for the study of the pyritization. 


MAX ROESLER 


1831 


East Mine 

The East Mine itself lies east of Firmeza, at an elevation of from 440 
to 700 ft., but it cannot be considered apart from the small cut just to 
the north at about 800 ft. elevation, known locally as the North Mine. 

The large orebodies of this mine are made up of specularite and 
magnetite, with much epidote quartz and garnet. They lie in the lower 
levels of the mine around bosses of aplitic granite, in diorite and diabase 
porphyry. Fig. 18 is a photograph and Fig. 19 a microphotograph 
of a lime-iron garnet rim along a small aplite dike, in recognizable 
diabase porphyry. It shows the entire ability of the mineralizers that 
accompanied the aplite to garnetize the diabase. 



Fig. 24. —Photograph of a Drawing Made with a Camera Lucida, from a 
Thin Section of a Specimen from West One Mine. It Shows a Diabase Por¬ 
phyry, Partly Replaced by Magnetite (Solid Black). The Phenocryst is 
Plagioclase. The Lath-Shaped Crystals Are Plagioclase. The Ground- 
mass IS Granular Magnetite and Chlorite. 

(In the upper half of the drawing the interstitial magnetite has been left out.) 

Fig. 26 is a microphotograph of a thin section of a completely epido- 
ized and silicified diabase. The specimen comes from within 2 ft. to 
the one shown in Fig. 15. The two show successive stages in the hydro- 
thermal metamorphism. 

In the upper levels, extending toward the North Mine workings, 
are several included sheets of completely marmorized limestone. The 
North Mine workings, now abandoned, show remnants of orebodies. 
This ore is different from any found in the mines so far described. Well- 
developed rosettes of specularite blades in garnet quartz matrix; well- 
crystallized epidote in abundance; coarse quartz; much recrystallized 
calcite; in short all the components are found of a typical contact-meta- 
morphic deposit in limestone. 





1832 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


In the East Mine, as in the others, later andesitic and dioritic dikes 
are in evidence. A northwest-southeast fault, pitching to the northeast, 
has cut the ore and aplitic granite as well as the older rocks. It has 
brought the most basic of the granitic rocks, the quartz-bearing diorite, 
in contact with the ore. That the specimen described as a wall rock of 
the East Mine by J. F. Kemp^® came from this mass of quartz-bearing 
diorite seems probable. The rock in which the ore is found is of a much 
. finer grain. 

In the East Mine itself there is no evidence that limestone had any 
share in forming the orebodies. In the workings known as the North 
Mine, limestone is without doubt the host rock of the orebodies. 


EAST 

MINE 


Fig. 25. 






The ore in the main workings, with the associated granitic rocks, 
was formed at centers of intense mineralization. The ore deposits of 
the North Mine were formed at a greater distance from the centers of 
mineralization. The aplite dikes in the terrane between the two are the 
filling of the fissures through which the solutions traveled. 


Chicharron (North East) Mine 

Located about ^ mile northeast of the East Aline and now entirely 
idle, are the workings of the old Chicharron Aline. This mine is well 
noith of the zone in which most of the mines lie, and in some respects 
differs from the others. 


Op. cii., p. 15. 



















MAX ROESLER 


1833 




Fig. 27.— Ore from Chicharron Mine. X 18. Magnetite—black. 

Wollastonite—white. 

magnetite, with interstitial wollastonite in small amounts (Fig. 27). 
A. C. Spencer describes this occurrence as follows:"^® 

“At this place the magnetite seems to be an intrusive dike cutting across a mass 
of crystalline limestone into which it sends a short apophysis.” 


Fig. 26.—Diabase Porphyry Completely Replaced by Epidote and Quartz. 
From East Mine. X 18. Quartz—light. Epidote—dark. 

replaced by magnetite, wollastonite, and epidote. The brook bed follows 
along the bottom of the cliff, and with an overgrown talus pile, separates 
the cliff from a mass of marble. Cutting the marble is a dike of 


The face of the mine is a cliff of diabase, over which the water of the 
Benevolencia River falls. This diabase is more or less mineralized, and 


Op. cit., p. 80, 







1834 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


The magnetite probably formed a dike, instead of a more diffuse form of 
deposit, because while the temperature was high, the pressure was not. 
As a result, the diffusive power of the mineralizers was not great, although 
they could form high-temperature minerals. 

In the Chicharron Mine, also, the later dikes are in evidence. 

Estancia Mines 

To the east of East Mine, in the mineralized zone, lies Estancia Hill. 
All around the hill at from 700 to 800 ft. elevation lie mine workings. 
The ore in these workings is either magnetite and specularite replacing 
diabase, or it is the hematite-garnet-calcite combination that is eloquent 
of contact-metamorphic limestone, though no limestone is left. Around 
most of the hill, and all of the south side, is a railroad track at an elevation 
of about 500 to 550 ft., and it is nearly all cut in a porphyritic granite, 
in which micropegmatite predominates. In the valley north of Estancia 
Hill granite is exposed along the trail. The dump of an old tunnel run 
into Estancia Hill for 600 ft. at an elevation of 695 ft. is granite, and A. 
W. Gaumer, the Juragua Iron Co.’s chief engineer, informed the writer 
that all the tunnel was in the same rock. South of the railroad track 
runs the lower trail to Concordia, and it is all in diorite, or coarse diabase, 
which has been mapped as diorite. 

All this evidence seems to indicate that a sheet of porphyritic granite 
intruded into diabasic rock with included marble, to form a sill. The 
orebodies at the upper contact of the granite formed in that rock to which 
the mineralizers had access. 

Concordia Mine 

This, the most easterly of the Juragua Iron Co.’s mines, offers no new 
evidence. It is the lowest of the mines, being at an elevation of from 300 
to 450 ft. The rock and ore association is magnetite in diorite with 
granite near by. 

The ore deposits are lenticular, and as a rule lie in an almost horizontal 
position. No limestone is in evidence. 

VIII. GEOLOGIC HISTORY 

The evidence from which the geologic history of the Firmeza district 
must be deduced is scanty. Almost all the field work was done in the 
immediate vicinity of the mines, and little search was made in the sur¬ 
rounding country for evidence which might give completeness to the 
geologic history. Enough material was found to make possible a 
sequential arrangement of the geologic events that produced the present 


MAX ROESLER 


1835 


topographic, petrologic, and mineralogic features of the district. These 
geologic events will be discussed in the order of their occurrence, as 
follows: 

1. Sedimentation. 

2. Igneous cycle (including ore deposition). 

3. Uplift with tilting and erosion. 

4. Deposition of coral limestone. 

5. Emergence. 

6. Submergence. 

Sedimentation 

The formation which appears to be the oldest in the district is the 
marble. As has been shown in the discussion of the rocks, this marble 
is Mesozoic, and probably Cretaceous in age. The constituents of the 
floor upon which the limestones now represented by marble were depos¬ 
ited, cannot be determined; nor is it possible to estimate the thickness of 
these early sediments, because of the lack of any continuous section. The 
limestone found at the highest elevation is a tuff-limestone. Because of 
its position it may be considered as the youngest of these early sediments, 
and because of the volcanic fragments embedded in it at the time of its 
deposition, it may be considered as representing the connecting link 
between the period of sedimentation, and the initiation of the igneous 
cycle. 

Igneous Cycle 

The igneous cycle began with a period of volcanic activity, to which 
the clastic igneous rocks of basic nature bear witness. These volcanic 
rocks form the southern slopes of the Sierra Maestra range, and the tops 
of some of the foothills. They contain remnants of interbedded lime¬ 
stones, and must have formed contemporaneously with the latter part of 
the period of sedimentation. 

The next event was the invasion of these volcanic rocks and sedi¬ 
ments by a magma of basic composition. Of this “parent” magma the 
present representatives are the diabasic and dioritic rocks. These rocks 
were left in their present position partly by the chilling of the magma, 
and to a lesser degree, by intrusion into the sediments and volcanic rocks. 

The invasion of basic magma was followed by a long period of differ¬ 
entiation. During this period the liquid residue in the magma chamber 
became more acidic, and charged with mineralizers. This acidic liquid, 
with its burden of mineralizers, invaded the earlier, chilled, basic, igneous 
rocks in the form of a granitic batholith. 

Further differentiation, resulting in a concentration of the mineral¬ 
izers, ended in the injection of the mineralizers, with admixed rock 
material, into cooling cracks in the basic rocks above the batholith. 


1836 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


There followed a separation of the highly heated mineralizers from their 
admixed rock material, which resulted in the formation of the ore deposits 
and the aplitic and pegmatitic apophyses. 

It is uncertain to what part of the igneous cycle the marmorization 
of the limestone should be ascribed, because all the marble exposures are 
near or in igneous intrusive rocks, which range from diabase to granite. 
Any one of these may have been competent to produce the marmoriza¬ 
tion. It seems probable, however, that because it was the earliest, the 
invasion of the diabasic magma is responsible for the greater part of the 
marmorization. 

What events were taking place at the surface during the igneous cycle 
is a question to which no answer has been found. The formation of cool¬ 
ing cracks, however, in the basic igneous rocks, seems to indicate that 
they were not very far from the surface at the time of ore deposition. 

The last episode in the igneous, cycle was the intrusion of basic dikes 
into fissures formed in all the igneous rocks and their associated ore 
deposits. 

Uplift, Tilting, and Erosion 

Because of the almost complete marmorization of the older limestones, 
their bedding is difficult to determine. But the pitch of the extrusive, 
and the few visible remnants of stratification in the marble, indicate a 
definite dip to the southeast. Evidence of uplift is found in the fact that 
limestone occurs at elevations up to 1,400 ft. above sea level. 

As has been shown in the discussion of the areal geology, there is no 
conclusive evidence as to the exact time relation between the igneous 
cycle and the period of uplift and tilting, but because pressure is to a 
certain extent a function of depth, it seems probable that the ore deposits 
were all formed in an approximately horizontal plane. Their present 
position along an inclined plane would, in that case, be some measure 
of the differential elevation. Meager and inconclusive as the evidence is, 
it must be considered, and until evidence to the contrary is found, the 
uplift and tilting should be regarded as later than the igneous activity. 

The coral limestones themselves show no evidence of tilting and this 
fact places the tilting as older than the coral limestones—that is pre- 
Pleistocene. Emergence has, however, continued. 

Fragments of iron ore in the base of the later coastal limestones prove 
that this period of uplift was accompanied by erosion sufficient to cut 
into the ore deposits. 

So far as the ore belt is concerned, the later record is one of continued 
erosion. Whatever else may have happened to that part of the district, 
no record remains except one of superficial alteration and erosion. The 
coral limestones and the valley topography show that dynamic forces 
were not entirely quiescent. 


MAX ROESLER 


1837 


Deposition of Coral Limestone 

The deposition of the Pleistocene-Recent coral limestone began when 
the land was about 350 ft. lower than at present. Since then there has 
been oscillation with predominant emergence. 

Emergence 

The sea-cut cliffs in coral limestone, rising in terraces from the coast 
to an elevation of 350 ft., are evidence of the periodic emergence of the 
land since deposition of the limestone began. What the extent of the 
emergence was cannot be determined on the evidence in the district, 
because it has been masked by the most recent geologic event— 
submergence. 

Submergence 

A. C. Spencer,'^^ judging from other parts of the island, places the 
amount of the submergence at from 40 to 70 ft. If the thickness of the 
fluviatile deposits in the east-west valley could be determined, it would 
give an accurate measure of the amount of submergence in this district. 

For reasons that have been discussed in detail under the interpretation 
of the topography, the writer believes that this submergence represents a 
movement of the sea. 

The geologic history of this district is a record of quiet activity. There 
is no regional metamorphism or profound fracturing, such as would be 
expected if vast diastrophic movements had taken place. The only 
metamorphism that has left a record was due either to igneous or to 
superficial causes. The only fracturing recorded is the result of the 
shrinkage of igneous rocks in cooling, and gives evidence of little or no 
local movement. Igneous forces, acting through long periods of time, 
dominated the rock formations. Slow uplift, alternating with periods 
of almost complete quiet, and accompanied by much erosion, formed the 
topographic features. 

IX. ECONOMIC APPLICATION 

Any geological investigation of more than a purely academic interest 
must answer some questions of a commercial nature. The present study 
of the ore deposits of the Firmeza district, by its inquiry into .their origin 
and extent, is able to answer certain questions which are of economic 
interest. These questions refer to the continuation of the deposits in 
depth, a possible change in their composition if they do extend downward, 
and the favorable locus for the search for more ore. 


Op. ciL, p. 34. 








1838 


IRON-ORE DEPOSITS OF THE FIRMEZA DISTRICT 


Continuation of the Orebodies in Depth 

Since the mineralization came‘from below, from the granitic massif, 
there is no reason to believe that the ore will not extend at least to the 
granite. On the other hand, there is no reason to believe that the 
separation of the mineralizers from the granite was incomplete, so 
that no ore can be looked for in the granite. Where the ore lies on top 
of sheet-like granitic masses, like the Estancia and Loma Alta deposits, 
a definite limit in depth is in sight, but in workings where the massive 
granite is not in evidence, extensive development in depth seems probable. 

Character of the Ore in Depth 

The pyritization in the ores at Firmeza has made the owners of the 
ore deposits fear that the ores would change to pyrite in depth. How¬ 
ever, the pyritization is later and independent of depth. There is no 
reason to believe that the ores found at greater depth will be any higher in 
sulphur than those now being mined in the lower levels of the larger 
mines. The lower sulphur content of the ores close to the surface is due 
to superficial oxidation of the pyrite. Below the level of surface oxida¬ 
tion the sulphur content may be expected to remain fairly constant. 

The only change that seems probable is an increase in the proportion 
of magnetite to hematite, as the workings approach the deeper centers of 
mineralization. 

Favorable Locus for Exploration Work 

The problem of exploration work may be considered in two ways— 
positively and negatively. Both are of fundamental importance, 
although frequently the question of where to look for more ore is con¬ 
sidered, while the equally important question of where not to look for 
ore is neglected. It is just as necessary to discover in which localities 
the search for ore will be fruitless and therefore any exploration work 
would be valueless, as it is to know where the search for ore will be 
profitable. 

Obviously, rocks formed later than the ore, like the coastal limestone, 
cannot be expected to contain ore deposits. The granitic massif, from 
which the qre solutions are thought to have escaped, is also to be regarded 
as barren ground. 

On the other hand, the granitic apophyses, aplites and pegmatitic 
granite are the best guides as to the location of orebodies. It is their 
upper surface which merits the most careful search. 

Since the orebodies contain much magnetite, the magnetic survey 
is undoubtedly the best guide to their location. But a careful study of 


MAX ROESLER 


1839 


the formations is necessary to interpret such a survey, and to decide 
what areas of magnetic attraction are most valuable, and also what areas, 
in spite of a lack of this attraction, offer fields for development. 

The economic application of geologic evidence will be successful only 
as the interpretation of the geologic phenomena is correct. At the same ^ 
time the ultimate test of any geologic theory is its application in the 
field. 


Bibliography 

F. F. Chisholm: Iron-Ore Beds in the Province of Santiago, Cuba. Proceeding 
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C. Willard Hayes, T. Wayland Vaughan, and Arthur C. Spencer: Report on a 

Geological Reconnaissance of Cuba, made under the direction of General 
Leonard Wood, Military Governor, pp. 69-83 (Washington, 1901). 

R. T. Hill: Tertiary and Later History of the Island of Cuba. American Journal of 
Science, Ser. 3, vol. 48, p. 203 (1894). 

Geology of Jamaica. Bulletin of the Museum of Comparative Zoology 
at Harvard, vol. 34, pp. 92-100. 

J. F. Kemp: The Geology of the Iron-Ore Deposits In and Near Daiquiri, Cuba. 
Trans., vol. 53, pp. 3-38 (1916). 

James F. Kimball: The Iron-Ore Range of the Santiago District of Cuba. Trans., 
vol. 13, pp. 613-634 (1884-85). 

Geological Relations and Genesis of the Specular Iron Ores of Santiago 
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W. Lindgren and C. P. Ross: The Iron Deposits of Daiquiri, Cuba. Trans., vol. 
53, pp. 40-59 (1916). 

J. T. SiNGEWALD AND B. LeRoy Miller: The Genesis and Relations of the Daiquiri 
and Firmeza Iron-Ore Deposits, Cuba. Trans., vol. 53, pp. 67-74 (1916). 
Arthur C. Spencer: The Iron Ores of Santiago, Cuba. Engineering and Mining 
Journal, vol. 72, pp. 633-634 (Nov. 16, 1901). 

The Mayari and Daiquiri Iron-Ore Mines. Articles published in Iron 
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9, 1908). 

D. B. Whitaker: Letter in regard to production. Engineering and Mining Journal, 

vol. 97, p. 677 (March, 1914). 

H. Wedding: Die Eisenerze der Insel Cuba. Stahl und Eisen, vol. 12, No. 12, 
pp. 545-550 (June 15, 1892). 







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